Preprints
https://doi.org/10.5194/tc-2022-32
https://doi.org/10.5194/tc-2022-32
 
22 Mar 2022
22 Mar 2022
Status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

An assessment of basal melt parameterisations for Antarctic ice shelves

Clara Burgard1, Nicolas C. Jourdain1, Ronja Reese2, Adrian Jenkins2, and Pierre Mathiot1 Clara Burgard et al.
  • 1Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 2Department of Geography and Environmental Sciences, Northumbria University, Newcastle Upon Tyne, UK

Abstract. Ocean-induced ice-shelf melt is the highest uncertainty factor in the Antarctic contribution to future sea level. Several parameterisations exist to link oceanic properties to basal melt and force ice-sheet models. Here, we assess the potential of a range of existing basal melt parameterisations to emulate basal melt rates simulated by a cavity-resolving ocean model on the circum-Antarctic scale. To do so, we re-tune the parameterisations in a perfect model approach, and compare the melt rates produced by the newly tuned parameterisations to the melt rates simulated by the ocean model. We find that the quadratic dependence of melt to thermal forcing without dependency on the individual ice-shelf slope and the plume parameterisation yield the best compromise, in terms of integrated shelf melt and spatial patterns. The box, PICOP parameterisation and quadratic parameterisations with slope dependency yield basal melt rates further from the model reference. The linear parameterisation cannot be recommended as the resulting integrated ice-shelf melt is comparably furthest from the reference. When using offshore hydrographic input fields in comparison to properties on the continental shelf, all parameterisations perform worse, however the box and the slope-dependent quadratic parameterisations yield the comparably best results. Additionally to the new tuning, we provide uncertainty estimates for the tuned parameters.

Clara Burgard et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-32', Anonymous Referee #1, 22 Apr 2022
    • AC1: 'Reply on RC1', Clara Burgard, 08 Jul 2022
  • RC2: 'Comment on tc-2022-32', Xylar Asay-Davis, 09 Jun 2022
    • AC2: 'Reply on RC2', Clara Burgard, 08 Jul 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-32', Anonymous Referee #1, 22 Apr 2022
    • AC1: 'Reply on RC1', Clara Burgard, 08 Jul 2022
  • RC2: 'Comment on tc-2022-32', Xylar Asay-Davis, 09 Jun 2022
    • AC2: 'Reply on RC2', Clara Burgard, 08 Jul 2022

Clara Burgard et al.

Model code and software

Multimelt package (functions used to format data and implement the parameterisations) Clara Burgard https://github.com/ClimateClara/multimelt

Clara Burgard et al.

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Short summary
The ocean-induced melt at the base the floating ice tongues (ice shelves) around Antarctica is the highest uncertainty factor in the Antarctic contribution to future sea level. We re-tune, assess and compare the performance of several existing parameterisations to simulate basal melt rates on a circum-Antarctic scale, using an ocean simulation resolving the sub-shelf cavities as our reference. We find that simple quadratic slope-independent and plume parameterisations yield the best compromise.